A numerical investigation of the transport process of density currents over steep slopes and its implications for subsea cable breaks

Tropical cyclone-induced density currents may cause various environmental hazards, such as breaks in subsea cables and pipelines. This study aimed to simulate the formation and transport processes of sediment-laden density currents using the Reynolds-Averaged Navier Stokes model. The simulated velocity and excess density of density currents were validated using measurements from laboratory experiments. The model was then applied to simulate the flow field and transport processes of density currents in the Gaoping Submarine Canyon (GPSC), where approximately 17 cable-break events were recorded from 2006 to 2015. The inflow concentration required for the occurrence of density currents was approximately 21 g/L, which was much lower than the conventional threshold (40–45 g/L) or the critical internal Froude number for the occurrence of density currents. The analysis revealed that the local Richardson number determines the critical state for the occurrence of the density current. The velocities of density currents and estimated distributed load were approximately proportional to the inflow concentration when the inflow concentration exceeded a critical value. The estimated distributed load on cables also increased with river discharge and settling velocities of sediment particles. This study suggested that environmental factors and inflow conditions should be considered for optimal cable design.